1. Field of the Invention
The present invention relates to a robot cleaner system and a method of the robot cleaner to return to an external recharging apparatus. More particularly, the present invention relates to a robot cleaner system including a robot cleaner having a rechargeable battery and an external recharging apparatus for charging the battery, and a method for the robot cleaner to return to the external recharging apparatus.
2. Description of the Related Art
Generally, a robot cleaner automatically travels around an area of a predetermined range to clean a floor or a surface by drawing in dust and impurities without requiring a user's manipulation. The robot cleaner measures distances therefrom to obstacles such as furniture, office supplies and walls in the cleaning area and travels around without colliding with the obstacles using information on the measured distance, thereby performing a cleaning work as instructed.
The robot cleaner includes a battery for supplying electric power for driving. Rechargeable batteries are generally used to reuse the battery after being exhausted. Therefore, the robot cleaner needs an external recharging apparatus for charging the battery with electric power. The robot cleaner system includes the robot cleaner and the external recharging apparatus.
In order for the robot cleaner to automatically return to the external recharging apparatus, the robot cleaner needs to correctly perceive a location of the external recharging apparatus.
Among various methods for the robot cleaner to perceive the location of the external recharging apparatus and connecting with the external recharging apparatus, one example is as follows. The external recharging apparatus, having a charging terminal for connection with the robot cleaner, comprises a charging apparatus mark, whereas the robot cleaner comprises a mark sensor. Usually, a reflective optical sensor is used for the charging apparatus mark. The reflective optical sensor comprises a light emitting part and a light receiving part for receiving a light reflected from the charging apparatus mark. When the robot cleaner would return to the external recharging apparatus after finishing the cleaning work or after exhausting the battery, the light emitting part provided to the robot cleaner emits a light, and the light receiving part of the reflective optical sensor receives the light reflected from the charging apparatus mark mounted to the external recharging apparatus. Therefore, the robot cleaner recognizes the location of the external recharging apparatus and returns to the external recharging apparatus.
However, the reflective optical sensor, used for the robot cleaner system having the external recharging apparatus, is expensive. Further, the robot cleaner takes a long time to return to the external recharging apparatus because of a short distance that the optical sensor can perceive.